1. Field of the Invention
The present invention relates to a dynamic fringe pattern generating apparatus using liquid crystal and a method of manufacturing the same, and more particularly, a dynamic fringe pattern generating apparatus for generating a fringe pattern used for a three-dimensional surface profilometer by using a single liquid crystal sample and by simultaneously controlling phase-shifting of the fringe pattern and a change in period of the fringe pattern by selectively applying a voltage and a method of manufacturing the same.
2. Description of the Prior Art
A three-dimensional surface profilometry (optical surface profilometry) is a technique capable of measuring position information and depth information of a surface of an object through an optical method. Since the technique has an advantage of being able to speedily obtaining three-dimensional surface profile information without a direct contact with the surface of the object, recently, the technique has been widely applied in the fields of medical industry, robotics industry, and industrial measurement instrument.
A three-dimensional surface profilometer is an apparatus for measuring a surface profile by calculating depth information from a distorted image of a fringe pattern irradiated on a surface of an object. FIG. 1 is conceptual diagrams illustrating principles of operations of the three-dimensional surface profilometer. Referring to (a) of FIG. 1, the three-dimensional surface profilometer is configured to include a projector 15 which irradiates a fringe pattern on a surface of an object 13 as a measurement object and a unit 17 which images the surface of the object 13 irradiated with the fringe pattern. The irradiation point of the fringe pattern and the image point are designed to be separated from each other, so that the surface profile can be measured from a degree of distortion of the irradiated fringe pattern, (b) of FIG. 1 illustrates the object 13 which is to be measured and a reconstruction area which is to be reconstructed. The projector 15 sequentially irradiates fringe patterns having a plurality of frequencies on the surface of the object 13.
Next, the fringe pattern which is irradiated on the surface of the object and is distorted is imaged by using a camera 17. (c) of FIG. 1 illustrates images of the fringe patterns irradiated on the surface of the object. The degree of distortion of the fringe pattern is measured from the image, and surface information of the object is calculated based on the degree of distortion of the fringe pattern, so that the surface profile is reconstructed as illustrated in (d) of FIG. 1.
In order to improve performance of the above-described three-dimensional surface profilometer, a 4-step phase-shifting method and a multi-spatial frequency method are frequently applied. The phase-shifting method is frequently used in order to reduce uncertainty of reconstruction phase information caused by a noise signal due to ambient light and a cosine function. The multi-spatial frequency method is frequently used in order to increase a measurable depth range and to improve measurement accuracy. Therefore, a three-dimensional surface profilometer in the related art uses optical components such as a digital micro-mirror device (DMD), an acousto-optical modulator (AOM), and a spatial light modulator (SLM) and apparatuses such as a projector. However, since the optical components are expensive and have a considerable volume, there are problems in terms of miniaturization and commercialization.